.square {
  background: #fff;
  border: 1px solid #999;
  float: left;
  font-size: 10vh;
  font-weight: bold;
  line-height: 10vh;
  height: 10vh;
  margin-right: -1px;
  margin-top: -1px;
  padding: 0;
  text-align: center;
  width: 10vh;
  cursor: pointer;
  
}

.square:hover {
  background: #f3f3f3;
  cursor: pointer;
}

.square:focus {
  outline: none;
}

.square.black {
  color: black;
}

.square.red {
  color: red;
}

.square.winner-line {
  background-color: #66ccff;
}